Field
An electrode wound element for a non-aqueous electrolyte rechargeable battery, a non-aqueous electrolyte rechargeable battery including the same, and a method of preparing the electrode wound element for a non-aqueous electrolyte rechargeable battery are provided.
Description of the Related Art
Research on a polyvinylidene fluoride (PVDF)-based fluorine resin as a matrix polymer of a gel electrolyte for a rechargeable lithium ion battery has been actively made. For example, technology for forming a porous layer made of the PVDF-based fluorine resin on the surface of a separator is widely known. In this technology, the porous layer is, for example, formed on the surface of the separator in the following method.
A first method includes preparing a slurry by dissolving a fluorine resin in an organic solvent such as NMP (N-methyl pyrrolidone), dimethyl acetamide, acetone, or the like, coating the slurry on a separator or an electrode, and phase-separating the fluorine resin by using a poor solvent such as water, methanol, tripropylene glycol, or the like or vapor thereof to form a porous coating layer in which the fluorine resin is made porous.
A second method includes preparing a thermal slurry by dissolving a fluorine resin in a heating electrolytic solution using a solvent such as dimethyl carbonate, propylene carbonate, ethylene carbonate, or the like to prepare heated slurry, coating the heated slurry on a separator or an electrode to prepare a coating layer, cooling down the coating layer, and transferring the fluorine resin into a gel (a porous layer swollen by an electrolyte solution).
However, the separator having the PVDF porous layer on the surface in the above method has insufficient slipperiness when compared to a separator having no porous layer and easily becomes electrostatic and thus is difficult to handle in a preparing process. Specifically, when the separator is overlapped with belt-shaped positive and negative electrodes for a wound element, the wound element becomes deformed due to the insufficient mutual slipperiness of the separator. When the wound element is deformed, the wound element is difficult to be inserted into a case. In addition, a non-aqueous electrolyte rechargeable battery using this deformed wound element may have an insufficient cycle-life.
Furthermore, the separator having the polyvinylidene fluoride porous layer on the surface according to the aforementioned method has insufficient adherence to an electrode, and particularly, the insufficient adherence problem tends to be severe when the separator includes a heat resistance filler to improve heat resistance. When the separator has insufficient adherence to each electrode, a wound element may has a problem of easy expansion (so-called a problem of cycle expansion) as charge and discharge proceed.
In contrast, Japanese Patent Laid-Open Publication No. Hei. 10-110052, Japanese Patent Laid-Open Publication No. 2012-190784, Japanese Patent Publication No. 2010-538173, and Japanese Patent Laid-Open Publication No. 2011-204627, for example, disclose technology for using fluorine resin particles or ceramic particles. Japanese Patent Laid-Open Publication No. Hei. 10-110052 discloses a method of protruding a part of the fluorine resin particles out of a porous film separator. Japanese Patent Laid-Open Publication No. 2012-190784 discloses a method of including the ceramic particles inside a separator. Japanese Patent Laid-Open Publication No. 2010-538173 discloses a method of charging a part of micropores in a non-woven fabric with the fluorine resin particles. Japanese Patent Laid-Open Publication No. 2011-204627 discloses a method of preparing a negative electrode by using aqueous slurry in which a polymer complex of a fluorine resin and a polymer having an oxygen-containing functional group is dispersed. However, these methods do not solve the aforementioned problem at all.